Bending apparatus and method of producing bent strip material



0 Jan. 10, 1928. 1,656,003

G. F. JOHNSTON BENDING APPARATUS AND METHOD OF PRODUCING BENT STRIP MATERIAL Filed Jan. 14. 1924 2 Sheets-Sheet; 1

Jan. 10, 1928. 1,656,003

G. F. JOHNSTON BENDING APPARATUS AND METHOD OF PRODUCING BENT STRIP MATERIAL Filed Jan. 14, 1924 2 Sheets-Sheet 2 49 A? Patented Jan. 10, 1923.

usirsn STATES PATENT OFFICE.

F. JOHNSTON, OF WAUWATOSA, WISCONSIN, ASSIGNOR T ALLIS-GHALMER$ MANUFACTURING COMPANY, OLE MILWAUKEE, -WISGOINE3IN, A CORPORAELION' U1? DELAWARE.

BENDING APPARATUS AND METHOD OF PRODUCING BENT STRIP MATERIAL.

Application filed January 14, 1924 Serial No. 685,946.

This invention relates in general to metal bending, and it has particular relation to apparatus and methods of special utility in the production of strip material bent in edgewise fashion.

In bending strip material, especially material of large size, in an edgewise manner, there is a crowding over or enlargement of the material adjacent the inner edge of the bend and a tendency toward stretching or reduction of the cross section of the material adjacent the outer edge of the bend. Where it is necessary or desirable to preserve the same thickness of the i'natcrial throughout, as in thecase of wound coils for electro magnets 01 dynamo-electric machines, etc., this enlargement of the material at the inner side of the bend is a decided disadvantage, for it requires a subsequent expensive op eration to reduce or reform the enlarged wedge-shaped section, usually through cutting, grinding or swagin The present invention contemplates or includes the production of articles formed from distortible stri a material es Jeciall of relatively large size or width, bent edgewise at one or more points, and wherein excess thickness oi. material produced at the inner edge of bend during the bending operation, is removed by an operation directly associated with the bending operation; and, likewise, the invention contemplates the performance of the combined operations of bending and reducing the bent material to desired final shape at a considerably reduced cost and in considerably less timethan is required for the several operations of bending and trimming the material at the bend, as practiced in the past.

An object 0'? the present invention is to provide an improved method and apparatus especially adapted for producing bent strip material wherein excess thickness formed at the inner side of the bend is reduced to desired dimensions.

A further object oi? the present invention is to provide an improved. method and apparatus especially adapted for producing objects formed from bent strip material, and in accordance with which the material may be bent and a portion of the excess thickness termed at the inner side of the bend may be reduced during the bending operation or a continuation thereof.

These and other objects and advantages are attained by the present invention, various novel features of which will be apparent from the description and drawings herein, disclosing embodiments and features oi. the invention, and will be more particularly pointed out in the claims.

In the accompanying drawings Figs. 1 and 2 are plan views of apparatus through which advantages of the invention may be realized, the apparatus being shown in several positions assumed during the opera tion of bending a section o'l strip material;

Fig. 3 is a detailed plan view of a section of material subjected to the bending operation;

Fig. 4: is an enlarged plan view oi? the ap paratus shown in Figs. 1 and 2; i

Fig. 5 is a front elevation of the device shown in Fig. i;

Fig. 6 is an end view of the device shown in Figs. 4 and 5; and

Fig. 7 is a view in elevation of a modilication, showing an arrrangement for permitting power operation of the bending device.

As shown in the drawings, 10 i1u1licates a section of strip material whose width considerably greater than its thickness, and which is to be subjected. to an ed gewise bending operation. 12 indicates a form or termin g block having its outer wall formed along an arc of 90 degrees and a radius required to produce the desired bending are at the inner side of the bent strip material. The form 12 may be shaped to provide a single 90 degree bend or, as shown, a plurality ot such bends, which arrangement would be an ordinary one for use in the formation of the turns of a coil. The form 12 mounted upon a support or table 13, preferably rotatable about an. axis i l which, in the case oi a form for producing turns oft a coil, is located at the center of such coil.

15 indicates generally a device or apps. ratus for effecting the operation of bending the strip material about the form .12 and, at the same time, producing the desired uniform thickness of the bent strip, this uniformity being secured by trimming or shaving the excess material from the inner edge of the bend. The device 15 includes a body portion 16, in the term of an upper jaw hav fill ing at its forward end two spaced extensions or arms 17, 18. A member is disposed at the lower side of the body portion 16, being pivotally carried by the body portion or member 16 and constituting, in effect, a lower jaw cooperative with the upper jaw 16. Bearin or wearing plates 21, 23 of relatively liard metal, are secured in opposed relation upon the opposed faces of arm 17 of the upper stationary jaw 16 and the lower jaw 19, respectively. As indicated, the upper jaw plate 21 is provided with a recess having a right angle shoulder at its inner side, as indicated at 2 1. During operation of the bending device 15 to impart the desired shape to the strip material 10. the latter is disposed in the recess 24- of the upper jaw plate and is held in position therein through the forcible bearing of the lower jaw plate 23 against the under side of the strip material, as indicated generally in Figs. 5 and 6.

Through the arrangement provided for insuring'pivotal adjustment of the lower jaw with respect to the upper jaw, it is possible to handle strip material of different thicknesses. As indicated, a saddle-shaped block 26 is mounted upon the upper side of the extension 17 of the upper jaw 16, the depending side arms of the saddle being apertured and carrying a pivot pin 27 on which the lower jaw 19 is pivotally mounted. The saddle 26 may be mounted in any one of several fixed positions upon the upper block, the adjusting and securing means comprising a wedge 28 which is slidable beneath the cross arm of the saddle on the upper side of the extension 17 to permit bodily separation of the pivot pin 27 and the lower jaw 19 carried thereby from the upper jaw. A bolt 29 has its head 31 bearing upon the upper side of the saddle 26 and passes through an elongated slot 32 in the wedge 28, the bolt being adjustably threaded in an aperture in the extension 17. The wedge 28 may be adjusted through a screw 31 carried thereby and threaded through an aperture in an abutment 35 mounted upon a portion of the upper jaw 16. As will be apparent, the screw 34 may be adjusted through the abutment 35, permitting the wedge to be forced to and from its position beneath the cross arm of the saddle, and the saddle and lower jaw 19 will then assume new positions in which they may be secured by tightening of the bolt 29.

The lower jaw 19 may be adjusted on its pivot 27 to cause the lower jaw plate 23 to forcibly cooperate with the under side of the strip material 10, by means of an adjust ingscrew 37 whose lower end abuts upon an end portion of the lower jaw 19 and which is threaded into the upper jaw 16, an operating handle 38 being secured to the screw 37 for rotating the latter. Operation of the handle 38 causes the plate 23 to forcibly grip or to release the strip material it). An adjustable abutment 11 is carried by a rod -12 which in turn is carried by the upper aw in, and is preferably integral with or secured to the abutment 35, a spring ii; being positioned between the abutment i1 and the under side of the lower jaw it), this spring being normally compressed and thus serving to bias the lower jaw to a position wherein the lower plate 23 is retracted from its operative position against the lower side of the strip material 1o. With this urrnngcment, it will be apparent that when the operating handle of the adjusting screw 3'? is shifted to draw the lower end of the screw upward, the spring 13 is cll'cctive to cause the lower jaw plate 23 to be retract ed from the upper jaw plate.

The forward end of the arm 17 of the upper jaw plate is provided with an extension -15 having an aperture e10, the extension 45 being of such thickness as to be readily insertible within an undercut recess or slot 41-7 in the outer wall of the form 12. As indicated, the arrangement is such that this extension -15 is preferably integral with the upper jaw plate 21, thus insuring that for handling strip material of dillereni widths or different arcs of curvature, all that is necessary is the substitution of an upper jaw plate of the required shape as to thickness and radius of bend. An imiicaied, with the device in operative position to bend a section of strip material, the axis of the aperture in coincides with the axis of curvuiure of the 90 degree are along which the form is shaped, a pin being inserted through the aperture in the form 12 and the aperture 4o to secure the bending device in operating relation.

A bending or forcing knee adjustably positionci'l on the under side of the extension 18 of the upper jaw 10, being held in operative position by means of a boil or screw 51 adjustable through an elongated aperture in the extension 18. The outer side of the bent knee or plate 19 is preferably formed as a straight edge, as indicated, which is in line with the inner wall of the recess 21- in the upper jaw plate 21, thus insuring that the outer edge of the strip material to be bent is in full contact with the bending knee and the inner wall of the recess 24 in the upper jaw plate during the bending operation.

The lower bearing surface of the upper jaw plate 21 is plain or shaped to fullv cugage throughout with the upper side of the strip material to be bent; while the opposed upper face of the lower jaw plate 2.; is formed at its leading edge with a more or less rounded head 53 extending acro the face of the plate and which bears loieibly against the under side of the strip material or plate if? is iii lid

tlll

ting tool memos the operation of the bending device, this head serves to stralghten or draw out or smeothen any irregularities in the strip device which passes through the axis of rotation oi the device. The cutting edge 54c projects upwardly to substantially the same eutent as, or preferably to a slightly greater eirtent than, the bead 53.

Assuming that the lower jaw plate 22-3 is notprovided with the cutting edge 53, as described hereinabove, the device may be used for the purpose of merely effecting the desired bending of the strip material.

l i ith the strip material 10 lying with its inner edge along the near side of thetorm 19;, Figs. 1 and 2, the extension oi the de vice 15 is inserted to and pinned in operatire position, the lower jaw 19 being retracted at this time, the tool being thus permitted to rotate about an axis through the center ot the 90 degree are through which the strip material is to be bent. At this time, the bending device occupies a position wherein the center line A A thereof occupics the position A in Fig. 1. By applying the required pressure to the operating handle 535 ol the device, the latter is swung in an illlthClOUltEWlSU direction about the center of the bending arc, during which operation the bending knee or plate 49 exerts the required pressure on the outer edge of the strip material to cause the latter to be bent along the outer surface ol? the form. When the tool .15 has reached the position wherein the center line ilr--i r thereo'lf occupies the position it the desired 90 degree curvature has been However,

9 imparted to the strip material. assiuning tor the moment that the cutting tool fi lv is not present, the thickness oi: the stri p material has been increased at the inner edge ot the bend, so that the material is now at a more or less wedge-shape which is thicker at the inner edge, the extent ot the enlarged portion being as indicated at 56 within the dotted line area, Fig. 3.

ll ith a lower jaw plate 23 having a cut- 5d, described hereinabove and .dlUWil in the drawings, and with the plate 23?) drawn up to operative position wherein it is in forcible engagement with the lower side of the strip material to be bent, the device 1.5 may readily be operated from the position [it to the position A during which operation the excess thickness of the material produced during the rotation of the device is formed just in front ot the center line AA otthe device, that is, substantially in th space between the drawing or smoothing bead 53 and the cutting edge 54. Hence, during the progress of the tool 15, the head 53 draws or straightens the bending strip and holds it firinly against the upper jaw plate, and immediately behind this bead an enlargement is termed as the actual bending of the strip occurs along the center line AA. However, as fast as this excess ma terial is produced, the cutting tool 5%, which is tired in position in so far as its approach and retraction from the upper jaw plate 21 is concerned, cuts or shaves this excess material from the under side of the strip material; and because the strip material is 'iorcibly held against the plain surface of the upper jaw plate 21, all. the increase in thicle ness appears at the lower side of the strip. The result is a strip bent to the desired shape with excess material, normally formed at the inner edge thereot, removed so as to leave the strip oi? substantially unit'orm thickness throughout the bent portion.

lrlowever, in certain cases, as in the present case, it is desirable that the bent strip be in the form ot a plurality oi. straight sections connected by a curved section, the desired movement of the ciiitting tool in an anticlockwise direction may not be suilicient to insure the removal oi the iinal portion of: the entire excess .material, indicated at 57, Fig. 3, the latter portion being that beyond the line corresponding to the position A. no cordingly, when. the bend. completed, that is, when the tool has lQElCl'lGd. the position. shown in. Fig. 2, .it may then be returned in a clockwise direction. so as to release the cutting tool from the chip, corresponding to the excess thiclmess being removed. from the strip material. The remaining portion 57 of excess thickness may then be removed in any suitable manner, as by means oi: ahand or power-operated chipping or milling tool.

As an additioiuil teature ot' the present invention, the device 15 may be provided. with improved means for removing not only the main portion ot the excess material as formed during the bending operation, but also the additional portion 57 of such excess material. As indicated, the lower jaw plate 23, with its straightening or drawing head 53 and its cutting tool at, are :arried by a traveling element or block 60 which is shittable upon the lower jaw plate transversely of the center line A-lr ot' the tool, a guiding arrangement, indicated at 61, being provided to insure straight line movement ot the bloclr 60 as the latter is forced to travel along the lower jaw plate. by means ot an operating screw 62 threaded through the traveling block, and rotatably mounted in end plates 63 secured tothe lower jaw plate.

A gear drive 64 is provided for the operating screw 62, the spindle 65 of this gear drive being arranged for operation by means of a crank handle or, as shown, through a sprocket 67, chain 68 and pinion 69 on the shaft of a motor 71 carried by the upper jaw plate 16.

In the operation of the apparatus last described, the traveling block 60 is adjusted to the position wherein the radially outer portion of the cutting edge of the tool it lies approximately in the center line A-A of the device, as previously described. The device may .then be rotated in an anticlockwise direction, with the lower jaw plate drawn up to bring the straightening head 53 and the cutting edge 54 into operative position relative to the strip material, until the device is brought to the position shown in Fig. 2, wherein the 90 degree bend has been imparted to the strip material and the cutting tool 54 has removed the major por tion of the excess material 56, the portion 57 of such excess material, however, remaining to be trimmed by a subsequent operation. ith the device 15 in this position, the traveling block 60, with its straightening bead 53and cutting tool 54, are reciprocated in such direction as to remove the excess material 57, power being applied to reciprocate the tool, by means of the motor 71. When the traveling block 60 has been reciprocated to a sufiicient extent to enable the cutting tool 54 to remove all of the excess material 57, the traveling block with its tools are again withdrawn to normal position wherein the forward edge of the cutting tool is in line with the center line A-A of the device.

With the bending and shaving operation thus completed, the device may be removed from the strip material by retracting ,the lower jaw, and removing the pin which connects the extension. 45 to the former block. The bent strip material may then be removed; or, in case it is desired that such strip be provided with a plurality of such 90 degree bends as in the case of forming a coil, a tool is removed to the adjacent former block about which the strip material is to be bent, and the operation described repeated. It will be apparent that by rotating the support 13 for the form 12 about its axis 14, any number of arc-shaped forms may be brought into operative position with respect to the bending device.

Where the labor of the combined bending and shaving operation is relatively great, this operation may be accomplished by means of a motor drive. As shown in Fig. 7, a support 81 may be mounted in fixed position relative to the form 12 or its supporting table 13, this support 81 carrying a motor 82 whose pinion 83 drives a gear 84 mounted upon a vartical reciprocating shaft 85. The lower end of the shaft 85 is provided with an extension 86 oi? such size as to fit within the alined aperture 46 of the extension 45 of the bending tool 1:") and the corresponding aperture in the form 12, under which conditions the tool 15 is held in operative position, with an operating arm or crank 87 on the shaft 85 having a driving pin 89 engaged in a recess in the upper side of the extension 17 of the upper jaw plate Vith the parts in the position shown, it will be apparent that when power is supplied to the motor 82, the crank arm 87, through its driving pin 85), supplies the power required to shift the device 15 to the extent required to produce the desired 90 degree bend with an accompanying shaving operation on the strip material. \Vhen the operation completed. the shaft 85 and its crank arm 87 may be removed from operative position with respect to the form 12 and the bending tool 15, by means of the lever 90. The table 1 may then be rotated to bring an adjacent form into position wherein its axis is aimed with that of the shaft 85 and the parts arranged to effect the next bending operation. It desired, the table 13 may be stationary and the support 81 for the motor drive may be shiftable to bring the shaft 85 in line with any desired form.

Instead of the use of an additional motor 82 for producing the power operation of the bending tool, the latter may be operated to effect the bending and. the sharing operations, from the motor 71 which has been described as the source of power for producing the final shaving ot the portion 57 of the excess material at the bend. To cll'ect this operation through the motor 71, a train of gears connected to the motor pinion may be mounted upon the upper jaw plate 16, the final gear of the train, preferably provided with means for releasably clutching it to its shaft, being in such position as to mesh with a circular gear of gear section formed on and having its axis coinciding with the form 12. lVith the gears meshed and the drive operatively clutched to the motor pinion, it will be apparent that the tool will be driven by position A to the position A indicated in Fig. 2, after the effect of a planetary gear drive. \Vhen the bending operation is completed the drive connection between the gear train and the fixed gear segment on the form 12 may be released, and power may be supplied by hand or from the same motor 71 to drive the reciprocating cutting tool 5-1- to complete the removal of the excess material 57 011 the under side of the bent strip material.

\Vhile a 90 degree are has been described as the extent of a single bend accomplished with the apparatus herein described, obviously any less or greater bend may be loo lit]

the motor 71 from the lllll ltlt dill

ti it till tilt

mosaics lorrner and the trends may constitute parts cit one or more complete turns or a coil. It Will. be obvious that by the improved proe and apparatus herein described, bent strip material may be produced by a relatively simple operation and at a greatly re-- duced cost in the matters oi apparatueotime and labor.

lit should be understood that the invention med herein not lin'iited to the details oilt con struction and operation shown and described, for obvious modifications will be apparent to persons skilled in the art.

lt is claimed and desired to secure by Let tors Patentt- 'l. lln apparatus for bending material about a term, a device adapted to move relatively to the term and operative during said relative movement to bend said material and to remove therefrom excess thickness thereoi produced during; the bending operation.

9,. In apparatus for bending strip material, the combination oi: means for determining the shape to which said material is to be bent and instrumentalities for bending said material to said desired shape While permitting iJl'lCl'GdF-ZQ in thickness of said material at the inner edge oi? the bent portions and for reducing the thickness of bent portions of? said match at the inner edge thereof simultaneously with the bending of adjacent portions oi? said material ll. lo apps *atns for bending strip mate rial the combination eta term and a coin bincd bending and thiclniessreducing device, said device and form being relatively movable and operative to produce the desired bending}; oil said material and to re duce encess thickness produced on a portion cit said material bent during said relative movement.

d. in apparatus for bending strip material the combination of a term, and means tor accomplishing a combined bending and lllitltl]BBS-I'GilllClllQf operation on said mate-i riah said means and. said form beinp; relatively movable and said ineansbeinp; operative to term the desired bend and to reduce a portion of the excess thickness of said material during; the bending thereof and to remove another portion of the excess thickness subsequently to the completion of the bending operation.

5. in apparatus :tor bending strip material, the combination of a movable bending device. said bending device being cooperative With the material to cause said material to be bent to desired shape, and means operative with said bending device and cooperative "with bent portions of said material for re ducing errcess thickness of said material produced during the bending thereof.

6. ln apparatus for bending); strip materiab the combination of a 'l OSIN, and instrumentalities movable relative to said term and i. ln apparactus loi' bending; strip mate riah the combination ol a torc and movable element carrying a bending; device and ting; tool said bending device and. said cutting); tool being movable about said form. and adapted to cooperate With and bend said material against said term and to reduce err.-- cess thickness of said material produced dur ion the bending operation.

5%. in apparatus tor bendinp; strip material, the combination ot a term, and means movable about said term and comprising instrumentalities operative to bend the strip material about said l Ol'lll and to simultaneously shave from said material success thiclrnose at the inner side oil the bent portion.

9. in apparatus for bendin trip inateriah the combimition oi a to i, an element provided with a bending device and a cut" ting tool, said term and said element being relatively rnoiarble said bending; device b ing; adapted during said relative movement to bend said material. about said term, and said cutting tool being; adapted to remove a portion oi the excess thickness :lormed at the inner side of the portion of said material bent during said rela -ve inoven'ien t, and said cutting tool being; movable relatively to said bending device and adapted during said latter movement to remove from said material a :lurther portion o'l circa-ass thiclrness thereol.

'10. lo apparatus for bending strip mate rial, the coinbiiuition oil a term oi? curved outline, en element movable about s2 d torrn and provided with bending and cutting devices adapted to bend strip material about said form and to remove a portion of the excess thickness l'torined at the inner side of the bent portion of said material, and means for imparting to said cutting tool a :tur'ther movement in a substantially straight line to cause said tool to remove a iurther portion oi? said eircess thickness.

ll. In apparatus tor bending strip materiah the combination oil: a tornr, a carrier movable about said liornn bending she cut ting tools mounted on said carrien said bendin tool being cooperative With said term and adapted to bend strip material about said form, said cutting tool. beinp movable simultaneously 'Wi operative to remove 'l'roui said material a portion oi the one ss 'tl'iiclrnoss thcreol formed during the bending; operation, and said cutting tool having a movement relative to said bending tool and adapted therethi'ou 'h to remove an additional portion o i once hicliness or said material after the completion oil the bendinp; eper aticuu ill Ell

lid

Illlll lilo llll

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th said bending tool and ltd will

cutting tool is efiective to 12. In apparatus for bending strip material, the combination of a form, an element movable about said form and adapted to bend a section of the strip material about said form, said element comprising relatively movable members, an abutment on one member, a cutting tool on another member, and means for holding the strip material against said abutment and said cutting tool in proximity to the opposite side of sa d strip material whereby said cutting tool s adapted to remove excess thickness of sald material during the movement of said element.

13. In apparatus for bending strip material, the combination. of a form, an elementmovable about said form and adapted to bend a section of said strip material about said form and to remove excess thickness produced at the inner edge of the bent portion of the material, an abutment on one member, a cutting tool on the other member, a smoothing element on said latter member in advance of said cutting tool, and adjustable means for holding said strip material against said abutment and said cutting tool in operative proximity to the opposite slde of said strip material.

14. In apparatus for bending strip mate rial, the combination of a form, an element movable about said form and adapted to remove excess thickness produced at the inner edge of a bent section of the'material during the bending thereof, said element comprising relatively movable members, one of said members being pivotally mounted with respect to the other member, means for adjusting the position of the pivotalaxis of said pivoted member, a cutting tool on said pivoted member, and means for holding said cutting. tool in operative position relative to said strip material.

15. In apparatus for bending strip mate'- rial, the combination of a form, an element movable about said form and adapted to bend a section of said strip material about said form, a cutting tool carried by said element, means for holding said cutting tool in cutting proximity to said strip material, means for operating said cutting tool relatively to its carrying element whereby said cutting tool is caused to remove excess thickness from said strip;

16. In apparatus for bending strip mate rial, the combination of a form, an element movable about said form and adapted to bend a section of said strip material about said form, said element comprising relatively movable members, an abutment on one member, a cutting tool carried by the other member, and means for holding the strip material against said abutment and said cutting tool in cutting proximity to the opposite side of said strip material whereby said remove EXCESS thickness from a bent section of the material during the movement of said element and means for shifting said cutting tool with respect to its carrying member to cause re moval of a further portion of excess material from said strip.

17. In apparatus for bending strip material, the combination of a form, an element movable about said form and adapted to bend a section of strip material about said form, said element comprising relatively movable members, an abutment on one memher, a cutting tool carried by the other mcmber, and means for holding said strip material against said abutment and said cutting tool in cutting proximity to the opposite side of said strip material whereby said cutting tool removes a portion of the excess thickness of said material during movement of said element about said form. and means for shifting said cutting tool relatively to its carrying member to cause said tool to remove a further portion of excess material from said strip subsequent to the formation of a bent section of the material.

8 In apparatus for bending strip material, the combination of a form. an element movable about said form and adapted to bend a section of strip material about said form, a cutting tool carried by said element and operative during movement ot said element about said form to remove from said material a portion of the excess thickness at the inner edge thereof, and means for causing operation. of said cutting tool with respect to its carrying element to cause re moval of a further portion of excess thiclc ness of said strip subsequent to the formation of said bent section, said means comprising a motor carried by said element and drivingly connectible to said tool.

l9. In apparatus for bending strip material, the combination of a form, an element having bending and cutting devices, said element being movable into and out of operative relation with respect to said form and the strip material thereof and being further movable with respect to said form and said strip material when said element is in operative relation therewith, and power-applying means detachably connectible in driving re lation to said form and said adapted to effect therelative rotation thereof W excess thickness produced at the inner edge U in tit

of the bent sections, a driving motor, and means connectible in driving relation with said element and the several forms inter chaugeably and adapted to move said elcment about each of said ms to cause bend iug of said material and remomlv of excess thickness thereof at the bent portions.

521. fin improvement in the art of producbcnt material subject to increase .in thiclo no... during the bending operation, which comprises bending said material to desired shape While permitting increase in thickness thereof at the inner edge of the bent portion and removing during said bending operation a portion of the excess thickness of said bent portion produced during said bending operation.

522. An improvement in the art of producing bent strip material subject to increase in thickness during the bending operation, Winch comprises removing during the operation of bending said material a portion of the excess thickness formed at the bend, and removing another portion of the excess thickness subsequent to the completion of the bend.

523. An improvement in the art of produc ing bent strip material subject to increase in thickness during the bending operation, which comprises bending said strip mate rial While one face thereof is held against a relatively fixed abutment, and removing a portion of the excess thickness of the material from the opposite face of said strip material. during the operation of bending the same.

24. An improvement in the art of producing bent strip material. subject to increase in thickness during the bending operation, which comprises bending said material While one face thereof is forcibly held against a relatively fixed abutment, removing a portion of the excess thickness of the material from the opposite face thereof during the operation of bending the same, and removing the remaining portion of said excess material by an operation subsequent to the completion of the bend,

25. In apparatus for bending strip material, the combination of means for bending said material to desired shape, and means operatively associated with said bending means and operative upon portions of said material subsequent to bending thereof for reducing the thickness of said bent port-ions at the inner edge thereof.

26. In apparatus for bending strip material, the combination of means for bending said material to desired shape while permitting natural enlargement thereof at the inner edge of the bent portion, and a device operative during the bending of said. material for removing excess thickness of enlarged portions thereof formed during bending.

In testimony whereof, the signature of the inventor is affixed hereto.

GEORGE F. JOHNSTON.

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